The intermittent nature of solar energy is a major barrier to widespread use of solar energy.
There has been considerable research and development work in the area of storing solar energy. Options considered for solar energy storage include chemical storage batteries, pumped hydro systems, and thermal storage using a heat transfer medium (such as molten salt).
Chemical storage batteries, while technically able to provide storage, are too expensive for large scale use for the following reasons.
1. The initial capital cost is high per KWh of capacity.
2. Lifetime is short, requiring some replacements over a 20 year period.
3. Depth of discharge is typically in a range of 60-90%, requiring oversized battery bank.
4. Round trip efficiency has significant losses.
5. Exotic materials that are required for chemical storage may be limited and expensive.
6. Recycling of heavy/toxic materials is an additional cost at the end of life.
7. Careful management and/or maintenance of many individual cells adds additional cost.
8. Sensitive to over-discharge and over-charge.
Considerable research and development is still required on many fronts to produce a chemical storage battery which solves all of the above problems. There are also issues with other known solar energy storage options.
There is a need for an effective option for storing solar energy to meet customer demand which does not coincide with the time and quantity of incoming solar radiation. The need for an effective solar energy storage option is particularly the case for large scale solar energy plants that produce electricity that contributes to local, regional or national electricity supply networks.
The above description and the description of the invention described in International publication WO2012/009764 in the name of the applicant in later sections of the specification are not to be taken as an admission of the common general knowledge in Australia or elsewhere.